Electric valve converting system and excitation apparatus therefor



March 17, 1936. WTTAG 2,034,524

ELECTRIC VALVE CONVERTING SYSTEM AND EXCITATION APPARATUS THEREFOR Filed Aug. 25, 1933 Albert H. Mittag,

1:. H15 ttor'ney.

' '40 tain amount, it" interferes Patented Mn. '17, 1936 UNITED STATES ELECTRIC VALVE CONVERTING SYSTEM gall), EXCITATION APPARATUS THERE- Albert H. Mittag, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application August 25, 1933, Serial No. 686,751

17 Claims.

My invention relates to electric valve-converting systems and more particularly to new and improved apparatus for exciting the control elements of the electric valves of such converting systems.

Heretofore there have been devised numerous electric valve convertingsystems for transmitting energy between direct and alternating current circuits, direct current circuits of different 10 voltages, or independent alternating current circults of the same or diiferent frequencies. Many of these systems have included a distributor apparatus provided with a plurality of brush and segment elements 'eifective to render conductive 1 the several electric sequence to transfer the current between the several terminals of the load circuit of the system. In casethe load circuit of the apparatus constitutes a single alternating current motor it is cuse tomary todrive the distributor apparatus from the motor, while if the load circuit is an independent distribution circuit, the distributing apparatus may be driven by an auxiliary motor-at a speed dependent upon the frequency which it 25 is desired to supply to the .load circuit. Particularly in the case when such a distributonapparatus is driven by the motor which constitutes the load circuit of the system, it is essential that the live segment of the distributor is of exactly 30 the right length relative to the spacing of the brushes so that a segment w leave contact with a particular brush just as it makes contact with the succeeding brush. If there is a space in which neither brush makes contact with the live 35 segment of the distributor, this becomes a dead spot in which the motor cannot be started from rest. On the other hand, if the overlap during.

which both brushes are in contact with a live segment of the distributor is greater than i. cermaterially with the commutation of the current between the several electric valves. g

This is particularly true in the case of a motor energized from an alternating. current supply cit-- Under startingand low speed operating conditions, the commutation of the current between the valves is eifected by the supply frequency, that is, by the supply voltage periodically falling to zero, and the question of over- 50 lapping of the brush'contacts of the distributor segments is relatively unimportant. At higher speeds, however, the counter-electromotive force generated, by the motor isthe principal factor in the commutation of current between the elec- 55 tric valves and the complete transfer of the curvalves in a predetermined cuit to an alternating including a distributor apparatus, which will preslightly rent between the valves must be eifected within a definite commutating angle referred to the load current, or it cannot be completed at all. Under these conditions it is very important that there should not be excessive overlap in the contacting. periods pf the brushes controlling the valves between which the current is to be commutated.

It is an object of my invention, therefore, to provide an improved electric valve converting systemand an excitation apparatus therefor which will overcome the above-mentioned disadvantages of the arrangements of the prior art and which will be simple and reliable in operation.

It is another object of my invention to provide an improved electric valve converting system and a control distributor apparatus therefor which will facilitate the commutation of current between several electric valves under various operating conditions of the system. g 2

.It is a further object of my invention to provide an improved electric valve converting system and a control distributor apparatus therefor,

which will eliminate .dead spots on the distributor and which will, at the same time, avoid any 5,

overlapping of the brush and segment elements under normal operating conditions of the system.

It is a still further object of my invention to provide an improved method of operating an electric valve converting system for transmitting energy from an alternating current supply circurrent load circuit and vent the occurrence of any dead spots in the operation of the system, and which will at the same time facilitate the commutation of current between the valves under various operating conditions.

' In accordance with one embodiment of my invention, each of the terminals of a load circuit 40 is-interconnected'with the several terminals of a supply circuit through a group of one or more electric valves. ,Iirere is also provided a distributor apparatus provided with a brush and segment element for each group of electric valves,

the distributor being driven at a speed corresponding to the frequency which it is desired to supply to the load circuit. For example, if the load circuit comprises a single electric motor the, distributor may be driven directly from the motor. Instead of providing a single brush forleach group of valves, 2. pair of brushes are provided displaced in a space phase and the brushes of each pair may be shifted relative to each other to adjust the effective lengths of contact of the brush and segment elements or they may be selectively connected or disconnected to produce a similar result.

For, a better understanding of my invention,

' together with other and further objects thereof,

' proved distributor apparatus, while Figs. 2 and 3 show modified forms of apparatus. j

- Referring now more particularly tojig. 1 of the drawing, there is illustrated an arrangement for transmitting energy from a single ph e alternating current supply circuit E0 to a quarter phase alternating current motor I! of the syn chronous type, comprising armature phase windings l2 and I3, and a rotatable field windlngltxdetail United States Letters Patent No. 1,93'1,-'

The field winding 25 with the armature windings, as illustratedgin I4 may be connected in'series case it is desired to give the motor series characteristics, or in case shunt characteristics are desired,.the field winding may be separately excited in any well known manner. As illustrated,' the field winding I4 is connected between the electrical-neutrals of thephase windings l2 and l3, acircuitwhich carries unidirectional current, as will be explained more fully hereinafter. A'

' variable resistor l5,may be connected across the l1'and l8, and I9 and field winding 1 to regulate the speed-torque characteristics of the motor, in which case it is preferable also to include a reactor I6 in series with a parallel connected'winding It and reslstor l5. s

The terminals of the l2 are connected to the supply circuit through two groups of similarlyconnected electric valves 20, respectively; Similarly, .the ,armature phase winding I3 is connected to the supply circuit l0 throughtwo groups of elec trlc valves 2| and 22, and 23 and 24, connected to the circuit It) with a polarity opposite to that of electric valves |1-'-20,- inc. Each of the elec-! Y ary windings of the grid transformers 21, 28, '29 L and 304'respectively, although in some instances,

- vapor or gaseous electric discharge type.

, the 'se'veral electric valvesythe grids of the pairs off resistors 384i,

across the :primary windings of the grid transtrio valves I144, inc., is provided with an anode, a cathode and a control electrode or grid and may be of any of theseveral types well known in the art, although I, prefer to use valves'of the 'In :order to control the conductivity of ,valves l1-l8, i920, etc.',.are connected to their respective cathodes throiigh current limiting re sisters 25, negative bias batteries 26; and secondthe negative bias batteries 26 may be satisfactorily omitted. .Theprimary windings-oi the grid transformers, 21-30, inc., are-excited from the alternating current supply circuit l0 through.

any suitablephase adjustingmeans; such as an impedance phase shifting circuit 3|, and brushes 32 -35, inc., respectively, of a distributor -mecha-' nism 36. The'distributor 36 is provided with a single conductive segment 31 driven directly by the rotating memberfll of "the motor ll. The

inc., are preferably connected formers. 21-30, inc., respectively, to-stabilize or 5 stiflen-thejgridclrcufis and to providegja dlS- grid transformers.

my improved distributor alternating current circuit armature phase winding -.and '20, and 23 and itiatea rotation of the motor,

' mechanism 36. is effective to -valves connected to the terminals of the armature charge path for the leakage reactance of the The contact segment 31 is preferably of a length somewhat less than 180 electrical degrea, referred to the motor I I, so that, taking into consideration' the widthof the brushes, not more.

than one pair of electric valves of the groups between which current is commutated, is excited from the distributor mechanism 36 at any given instant. The distributor mechanism 36 is also provided with a plurality .of auxiliary brushes 3211-3511 electrically connected to the main brushes 32-35, inc., respectively, and normailydisplaced from the main brushes by a relatively small angle. These auxiliary brushes 3241-3511,

inc., are connected to a brush shifting yoke 42 for purposes to be explained hereinafter.

The general principles of operation of the above described apparatus for transmitting. en-' ergy from the alternating current circuit l0 to 'the motor II; will be well understood by those skilled in the art, or will be found explained in as-the feature of selectively energizing the grids 0 of the several electric valves from a source of alternating potential through vice. Assuming that the motor field winding I4 and the distributor mechanism 36 are substantially in the positions illustrated and that the phase shiftingcircuit 3| is so adjusted that the potentials impressed upon the primary windings of the several transf rmers 21-30, inc., are substantially in phase with the potential of the l0, it will be seen that the primarywindings of the grid transformers 28 and 30 are excited brushes 33 and 35, respectively, to render conductive the pairs of electric valves I3 and 20, and-23 and 24. These two groups of electric valves, I!

24, comprise a full wave rectifying circuit of which the unidirectional load circuit comprises the upper winding l3. The resultant produced by the current flowing in armature windings'l2 and |3 will be in such a direction as to exert a torque upon which, it will be assumed, is in a clockwise direction.

proximately electrical degrees, the grid transformer'30 will be deenergized at the brush 35 and the grid transformer 29 will be excited through the brush 34 of the distributor mechanism. [The esult is that the group on-conducting and the air of valves 2l-22 becomes conductlve to the armature winding l3.- Th e armature magnetomotiveforce of the. motor is thus advanced 90electrical degrees and a torque is produced onthe motor field an additional'90 degr e s. v In t manner current is successively co utated be een the several terminals of the-armature windings l2 and I3 to produces; rotating magneto-motivefprce and a rotation of the motor H. The distributor excite only those a commutating de'-' transfer current fronrthe' right-handportion to the left-hand portion of through their associated half of the armature winding l2, the field winding l4, reactor l6 and the right-hand portion of themotor armature magneto-motive force the motor field l4 and in,-

55" When 'the motor H has rotated through a'pe f valves 23-24 becomes M to rotate it through windings which are in apositive torque producwere broken without ing position with respect any particular instant.

In the above explanation, the auxiliary brushes fill-35a, inc., have been disregarded. Ii'thedistributor disc 01' the mechanism "had stopped in a position a few degrees tion illustrated so that to the motor field 4 at contact at the brush 33 completing that at the brush 32, it is seen that the'only pair of electric valves to be excited would be the valves 23 and 24, which areexcited through the brush 35. This would not provide a complete path acro'ss the supply circuit II with during which both pairs of electric valves'between which the current is commutated, are rendered conductive simultaneously. .Under starting conditions or lowspeed operating conditions of the motor, this slight overlap isnot important, as the commutation is effected by the supply voltage; thatis, the current in any particular pair or electric valves will be extinguished at the end of the particular hall cycleof At higher operating speeds, however, particularly when approaching synchronism, the supply voltage is no longer eil'ective to commutate the current between electric valves which, in the particular system illustrated, is accomplished by '0! commutation, there is a very definite limit to Y the time during vwhich'the transfer of current j may be eil'ected; that is, to the between the successive pairs of electric valves commutating angle. It current persists in the outgoing electric valve after this instant, the current cannot be interrupted at all and a short circuit results. Therefore, under these operating conditions it is important that there should be an inappreciable overlap," or preferably that the excitation to one grouD Of valves should actually be cut oil before it is supplied to the succeeding group'oi' valves. Under these conditions current will continue to how in the first pair of valves, however, it valves of the vapor or ga's'eo'us discharge type are utilized, because 01' the-inability of the grid circuit to interrupt normal current in the valves. This result may be secured by operating theyoke.42 to shiit the auxiliary brushes 320-156 until they are in phase coincidence with the main brushes 32-, inc., and thus completely ineiIective Under'these conditions the motor may be operated up to and beyond synchronism' and thecurrent will be 'commutated between the several electric valves in a normal manner.

In Fig. 2 is shown a modified form of the distributor mechanism 36 suitable for controlling the valves of a converting apparatus connected to a three phase alternating current load circuit or in advance of the posithe result that no current would flow in the armature windings l2 and i3 I and the apparatus would be on a' "dead spot.-

in Fig. l.

32 it would be made at the asdescribed above. Thus the the counter-electromotive i'orce generated by the rotation oithe field member l4. with this type brushes of '1 directly in well known and segment elemen alternating current motor. In this case the distributor comprises three main brushes 43, 44 and 45 and three auxiliary brushes 43a, 44a and 45a, respectively, and a single rotating segment 46 substantially less than 120 electrical degrees in length. With 120 electrical data spacing between the main brushes 43, 44- an is no overlap between the contacting periods of the several brushes, but that there is a dead spot of an appreciable width. Under starting and low speed operating conditions, however, the auxiliary brushes 43a, 44a and 45a are connected to their respective main brushes through a three pole switch mechanism 41. Under higher speed operating conditions the switch mechanism 41 may be opened to produce an ,efiect equivalent to the 5, it is clear that there shifting of the brushes in the arrangement shown Thus, the relationship between the brushes, of each pair may be modified either by adjusting their phase relation or by changing their electrical interconnections. If desired, of course, phase adjustment between the main and auxiliary brushes may be provided through the brush shitting yoke 42 in which brushes are mounted. i

In Fig. 3 is shown a still further modification of the distributor apparatus 38 suitable for application to a-four pole, three phase motor. In this case the main brushes 48, 49 and 50 are displaced 60 mechanical degrees or 120 electrical degrees, and a rotating element is provided with two contact segments 5i and 52, each somewhat less than 60 mechanical degrees and diametrically spaced. The auxiliary brushes 48a, 49a and "a are spaced the auxiliary substaxiflally diametrically opposite to the main brushes, 4! and 50, respectively, but are dis-' placed from the diametrical position by an angle substantially equal to the angle between the main and auxiliary brushes of lag conditions the switch mechanism 41 is operated to connect the main and auxiliary brushes and thus increase the efiective lengths oi. the segthe arrangement of Fig. ,2. in the previous arrangement, under startments, while at higher speeds, the switch-41 is i opened. It will be seen that, if the brush shifting yoke 42 is operated to place the auxiliary brushes diametrically sult is the opposite themain brushes, the reequivalent of shifting the auxiliary theapparatus shown in Figs. 1 and 2 phase coincidence with the main brushes, since, in the distributor of Fig. 3 the contact segments are diametrically opposite.

In the apparatus shown in thefigures and described above, the distributor apparatus is illustrated as having a stationary brush, or pair of brushes, for each of the terminals of the load circult, or motor, and a rotating contact segment for each pair of poles of the motor from which the distributor is driven. -It will be well understood, however, that the brush mechanism may be rotatable and that a single brush may cooperate with a pair of segments, the relationship between which may be modified by adjusting their phase or their electrical'ccnnection; or that a single brush, or pairthe contact segment stationary; or

of brushes, may be provided for each pair of poles of the motor and a plurality of segments, one for each terminal of the load circuit, all of which are mechan cal equivalents, all without departing from my invention. In its broadest aspects my invention comprises the use 01' a brush and segment element for each terminal of the load circuit per pair of poles. By the term brush is meant the combination of a single segment and a main and auxiliary brush or a single brush and a main and auxiliary segment.

While I hve described what I at present consider the preferred embodiments of my invention, it will. be obvious to those skilled in the art that various changes and modifications may be made Y tial, a a distributor without departing from my invention, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as'new and desire to secure by Letters Patent oi the United States,.is:

1. In acontrolled electric valve converting system, apparatus for exciting the control'elements oi the valvesuoi the system in a predetermined sequence comprising a source of control potensource and said control elements, and means; for

varying the effective length of contact of said brush and segment elements.

' 2. Ina controlled electric valve converting system, apparatus of the valves of the system in a predetermined sequence comprising a source of control potential, a distributor provided with a plurality of brush and segment elements interconnecting said source and said control elements, and means for varying the eflective length ot'the segment elements.

3. In a controlled electric valve converting sys--'- tem, apparatus for exciting the control elements of the valves of the system in a predetermined sequence comprising a source of control potential, a distributor provided with a segment of an angular length less than the conductive period or the valve controlled thereby and with a plurality or brushes interconnecting said source and said control elements,

. tem, apparatus for exciting the control elements.

and means for modifying the action of said brushes to extend the eilective length of said segment.

,4. In a controlled electric valve converting sysoi the valves of the system in a predetermined sequence comprising asource or control potential,

a distributor provided with a plurality of pairs of brushes, the brushes of each pair being interconnected and interconnecting said source and said control elements, and means for moving the tem, apparatus for exciting the control elements of' the valves of the system in a predetermined sequence comprising a source of control potential, a distributor provided with a plurality of pairs of brushes, the brushes of each pair being similarly displaced angular-1y upon said distributor, and means for selectively excitingthecon- .trol elements from said source through one or both brushes of each pair.

7.. In a controlled electric valve conve system, apparatus for exciting the control elements of the valves of the system in a predetermined sequence comprising a source of control potential said control elements from for interconnecting the and I,

, eral terminals of said provided with a plurality of v brush and segment elements interconnecting said each or said for exciting the control elements tend the eiiective length I 10. Ina controlled electric valve converting similar number of movable a distributor provided ments and pairs of brushes,

th a plurality of segcircuits iorenergizing said source through one the brushes 0! each pmr, and switch means modify the efiective length or said segment.

8. In a controlled electric valve converting system for transmitting energy from a supply circuit to a load circuit provided with a plurality of ter-fi minals, said system including a plurality of valves interconnecting said supply circuit with the sevload circuit, apparatus for exciting the control elements of the valves to render said valves. conductive in a mined sequence comprising a source I control brushes oteach pair to predeterpotential, a distributor provided with a brush and segment element for the valves associated with terminals for exciting said control elements from said source, and means'for varying the eil'ective length of contact of each of said 1 brush and segment elements. I

9. In a controlled electric valve converting system for transmitting energyfi'om a supply circult to a load circuit including niiterminals and alternating current motor having 12 pairs 01 field poles, said system including a plurality of valves interconnecting said supply circuit with the several terminals of said load circuit, apparatus for exciting the control elements of the valves to render said valves conductive in a predetermined sequence comprising a source of control potential, a distributor adapted to be driven by said motoi and provided with n' segments and m pairs of brushes interconnecting said control elements and said source, and means for m i ng the action of said brushes to exof said segments.

system for transmitting energy from a supply circuit to a load circuit including m terminals and an alternating current motor having n pairs of field poles, said system including a plurality of valves interconnecting said supply circuit with the several terminals of said load circuit, apparatus for exciting the control elements of the valves to-render said valves conductive in a predetermined sequence comprising a source of control potential, a distributor adapted to be driven by said motor and provided with 1: segments and m pairs of brushes interconnecting said control elements and saidsource, and the brushes of each 11. In a controlled electric valve converting cuit to a load circuit including ,m terminals and an alternating current motor having 11. pairs of field poles, said system including a plurality of valves interconnecting said supply circuit with theseveral terminals of said load circuit, apparatus for exciting the control elements of the valves to render said valves conductive in a predetermined sequence comprising a source of control potential, a distributor adapted to be driven by said motor and providedwith n segments and 11:. pairs of brushes, the brushes of each pair being displacedby a relatively small angle, circuits for exciting said control elements irom said source through a brush of each of said pairs, and switch means for interconnecting the brushes of each ments.

means for moving, pair relative to each other to increase the effective length of said segments.

12. In a controlled electric valve converting system for transmitting energy from a supply circult to a load circuit including m terminals and motor and provided with two segments and m pairs of brushes, said segments being displaced substantially 180" and the brushes of each pair being displaced by an angle slightly less than tact of said brush and segment elements.

14. The method of operating an electric valve converting transmitting energy from said valves are'rendered conductive for higher frequencies of said load circuit.

15 The method of operating an electric valve converting system for transmitting energy from an alternating current supply circuit to an alternating current load circuit provided with n terminals in which each terminal is interconnected with said supply circuit through one or more controlled electric valves, which comprises successively supplying excitation to the control elements of the valves associated with each terminal for a predetermined fraction of a cycle with respect to said load circuit when the frequency of relatively low with respect to that of said supply circuit, and decreasing the periods of excitation to the control elements of said valves for higher frequencies of said load circuit.

l6. The method of operating an electric valve converting system for transmitting energy from n alternating current supply circuit to an alternating current motor provided with n terminals in which each terminal is interconnected with said supply circuit through one or more controlled electric valves, which comprises successively rendering conductive the valves associated with each terminal for a predetermined fraction of a cycle with respect to the load circuit when said 17. In a controlled electric valve for exciting the control elements of the valves of the system in a predetermined sequence comprising a source of control potential, a distributor including a disc having one or more conductive segment contact elements,

one or more brush contact elements cooperating and segment elements interconnecting said source ments to vary the efiective length of contact of each brush and segment element.

ALBERT H. MITTAG. 

